Steam generating unit



Nov. 4, 1969 R. u. SHEIKH 3,476,090

STEAM GENERATING UNIT Original Filed Aug. 24, 1967 2 Sheets-Sheet 1RAMSEY U. SHE/KH INVENTOR.

BY ,;W 1; A n

N 1969 R. u. SHEIKH STEAM GENERATING UNIT 2 Sheets-Sheet 2 OriginalFiled Aug. 24, 1967 RAMSEY U. SHE/KH INVENTOR.

United States Patent Office 3,476,09h Patented Nov. 4, 1969 US. Cl.122478 6 Claims ABSTRACT OF THE DISGLOSURE This invention relates to asteam generating unit and, more particularly, to apparatus adapted toproduce steam from the hot products of combustion of a fossil fuel,including a combustion chamber having headers which are offset relativeto one another and a vertical superheater which is suported againstlateral movement by inclined rear wall tubes.

This application is a continuation of application Ser. No. 663,048,filed Aug. 24, 1967, now abandoned.

BACKGROUND OF THE INVENTION In the art of steam generation, it has beenthe general practice in the case of small boilers of the size that wouldbe used in a school building or a small manufacturing plant to use aso-called packaged boiler. This is a boiler which is absolutely standardin every respect, which is assembled in the factory, and which is smallenough to be shipped by railroad car to its ultimate destination. Inthis field, standardization has been carried to its greatest extent toobtain low price and adequate performance. On the other hand, most steamgenerating units which are used in large central stations are largeenough and expensive enough so that they not only can be custom designedfor each application but, because of their size, they must, of course,be assembled on the site. There is, however, a range of boilers ofintermediate size which are too large to be shipped in one piece byrailroad car and yet are not sufiiciently expensive to Warrant thecustom design which is used in larger units. Attempts to standardize inthis area have been somewhat successful, but many problems still presentthemselves. Many of these problems arise because of the fact thatassembly must take place in the field where precision equipment is notavailable to assure that the parts are put together with the necessarytolerances. Furthermore, the fact that the design must be simplified inorder to permit partial factory assembly and partial field erectionmeans that in the past, the boilers of the intermediate or industrialtype have been inefiicient and subject to many maintenance problems.Part of the problem lies in the fact that, because they are not asexpensive and as important as the central station unit, the maintenancepersonnel are not always of the best. These and other difiicultiesexperienced with the prior art devices have been obviated in a novelmanner by the present invention.

OBJECTS It is, therefore, an outstanding object of the invention toprovide a steam generating unit to which standardization can be readilyapplied for partial factory assembly and partial field erection.

Another object of this invention is the provision of a steam generatingunit wherein access to wall headers and drums is relatively simple.

A further object of the present invention is the provision of a steamgenerating unit which is simple in construction, inexpensive tomanufacture, and which is capable of a long life of useful service witha minimum of maintenance.

It is another object of the instant invention to provide a steamgenerating unit of intermediate size having an improved method ofsuperheat regulation.

With these and other objects in View, as will be apparent to thoseskilled in the art, the invention resides in the combination of partsset forth in the specification and covered by the claims appendedhereto.

DESCRIPTION OF THE INVENTION The character of the invention, however,may be best understood by reference to one of its structural forms, asillustrated by the accompanying drawings in which:

FIG. 1 is a vertical sectional longitudinal view of a steam generatingunit embodying the principles of the present invention,

FIG. 2 is a plan view of the unit,

FIG. 3 is a front elevational view of the unit,

FIG. 4 is a sectional view of the unit taken on the line IV-IV of FIG.1,

FIG. 5 is a sectional view of the unit taken on the line V-V of FIG. 4,

FIG. 6 is a perspective view of a portion of the boiler at theintersection of a side wall and the roof wall, and

FIG. 7 is a perspective view of the unit showing the area of theintersection of a side wall with the floor Wall.

Referring first to FIGS. 1, 2, and 3, wherein are best shown the generalfeatures of the invention, the steam generating unit, indicatedgenerally by the reference numeral 10, is shown as having a front wall11, a rear Wall 12, two side walls 13 and 14, a bottom wall 15, and aroof wall 16 defining a combustion chamber 17. Located rearwardly of therear wall 12 is a steam-and-water drum 18 joined by a plurality of heatexchange tubes 19 to a lower mud drum 21. Each side wall is made up of aplurality of tube panels which line the inner surface and face towardthe combustion chamber 17. In the present case, the wall 13, forinstance, is made up of two tube panels 22 and 23, the tubes of which ingeneral lie in the same vertical longitudinal plane. As will be evidentin the description of FIGS. 6 and 7, the side wall 14 is made up of twosimilar tube panels 24 and 25. The bottom, front, and roof walls areformed of water tubes which originate in the lower mud drum 21, extendgenerally horizontally to form the bottom wall 15, extend generallyvertically to form the front wall 11, extend generally rearwardly in asomewhat inclined manner to form the roof wall 16, and are thenconnected to the steamand-water drum 18. On the front wall 11 aremounted a plurality of burners 26 in pairs of two. In the preferredembodiment, as is evident in FIG. 3, six such burners are used.

The rear wall 12 consists of two vertical sections 27 and 28 joined byan inclined portion 29. A superheater 31 is provided consisting of aplurality of tube panels extending vertically in planes each of whichlies between the two vertical portions 27 and 28 of the rear wall 12.The panels of the superheater 31 extend through the inclined portion 29and are substantially supported thereby against lateral movement.

The superheater 31 is provided with two parallel transverse headers 32and 33 which are located below the bottom wall 15. Each tube of thesuperheater is of generally hair-pin shape with one end connected to theheader 32, and the other end connected to the other header 33. The bightof the tube lies adjacent the roof wall 16.

Referring to FIG. 4, it can be seen that the superheater headers areprovided with dividing walls to cause flow of steam seriatim throughseveral sections of the superheater. The header 32 is connected by apipe 34 to the steam-and-water drum 18 to receive saturated steamtherefrom. The other end of the header 32 is provided with an outletpipe 35 leading to the turbine or other apparatus using the steam.Extending across the header 32 are walls 36 and 37 dividing into tworelatively small end sections 38 and 39 and a relatively large centersection 41. The other header 34 is provided with a single dividing wall42 dividing the header into two equal sections 43 and 44. Mounted on theouter end of the section 43 of the header 33 is a desuperheaterapparatus 45 having an inlet pipe 46 connected to a source of water andcontrolled by a valve 47. A pipe 48 extends coaxially through thesection 43 and is welded at its inner end to the dividing wall 42. As isevident in FIG. 5, the pipe 48 is provided with a plurality of spraynozzles 49 each of which is directed into a superheater tube 51. Eachtube 51 is provided with a venturi-shaped tube liner 52 located at itsconnection with the header 33 to protect the welded connection betweenthe tube and the header from thermal shock.

As is evident in FIG. 6, the tubes making up the panel 24 of the sidewall 14 extend straight up past the roof panel and are connecteddirectly to an upper outlet header 53. The tubes making up the panel 25of the side wall 14, however, extend straight past the roof wall 16 andthen are bent inwardly to connect to an upper outlet header 54. Theheaders 53 and 54, therefore, are nonco-extensive and are displaced fromone another so that access may be had to either end of either header formaintenance and ease of assembly.

In the same way, referring to FIG. 7, the tubes of the panel 24 of theside wall 14 extend straight downwardly past the bottom wall 15 and areconnected directly to a lower inlet header 55, while the tubes making upthe panel 25, although they extend straight past the bottom wall 15, arethen bent inwardly in an inclined manner to connect to the lower inletheader 56. The headers 55 and 56 are, therefore, on generally the samehorizontal plane but are located laterally of one another so that theyare non-coextensive and non-coaxial, thus permitting access to eitherend of each header for maintenance and ease of assembly. Feeder tubes 57enter the headers 55 and 56 from the mud drum 21 for supply of water inthe side walls 13 and 14. In a similar manner, release tubes 58 leavethe upper headers 53 and 54 and connect to the steam-and-water drum forcarrying steam thereto.

One of the interesting aspects of the construction of the present steamgenerating unit is the manner in which air is brought to the burners 26.First of all, referring to FIG. 2, a regenerative air heater 59 receivesair from the forced draft fan 60 and carries it under the mud drum 21around the superheater headers 32 and 33, under the bottom wall 15 andup into the wind box of the burners 26. In this way, one need not worryabout leakage of gas through the bottom of the boiler because suchleakage of gas and air in either direction is entirely within the boilersetting and does not leave the casing.

OPERATION The operation of the invention will now be readily understoodin view of the above description. With air being provided to the burners26 by the air heater 59 and the forced draft fan 60 and with fuel beingprovided in the well-known manner to the burners, combustion takes placein the chamber 17. The hot gas flows rearwardly and upwardly passingover the surfaces of the upper portion of the superheater 31 until itimpinges on the upper section 28 of the rear wall 12. It then passesdownwardly through the inclined portion 29 of the rear wall whichportion is constructed with the tubes spread apart to permit suchpassage. The gas also passes through the upper section 28 and isdirected downwardly "by a baffle 61 formed by welding fins between a setof the tubes 19 to form a backpass. The gas is caused to flow back andforth over the superheater 31 and then over the main generating tubes19. Eventually, the gas passes outwardly through the air heater to thestack 62. Water is introduced into the steam-and-water drum 18 in theusual manner by a feed pump, passes downwardly through the tubes 19 tothe mud drum 21 and picks up heat on the way. It then passes upwardlyfrom the mud drum 21 back to the steam-and-water drum and is convertedto steam on the way. The tubes making up the bottom, front, and roofwalls as well as those forming the side walls and the rear wall allgenerate steam and cause it to flow to the steamand-water drum 18. Thesteam passes from the steamandwater drum through the pipe 34 to thesuperheater 31 where it is superheated and passed through the pipe 35for further use. The steam enters the super heater 31 through the pipe34 in the header 32. It first passes into the end section 38, passesupwardly through the tubes and back down to the header 33 into thesection 43. It flows lengthwise of the end section 43 of the header 33and leaves adjacent the dividing wall 42 and flows upwardly through thetubes and around down and into the central section 41 of the header 32.From there it flows lengthwise in a direction from the dividing wall 36to the dividing wall 37 where it passes upwardly through the tubes andback down again to the other section 44 of the header 33. It passeslengthwise away from the dividing wall 42 and then passes upwardly intothe tubes again and back down to the end section 39 of the header 32.From there it flows lengthwise away from the dividing wall 37 into thesteam pipe 35 for use in a turbine or the like. Now, while the steamresides in the chamber 43 of the header 33, it is subjected to adesuperheating action. Water flows into the desuperheater apparatus 45through a pipe 46 under the control of a valve 47. The water flows intothe pipe 48 which lies within the chamber and outwardly of that pipethrough its spray nozzles 49. The spray nozzles are directed into thetubes 51 causing a reduction, if necessary, in the superheated steamtemperature. The welded connection between the tubes 51 and the header33 is protected by the liners 52 against thermal shock.

It can be seen, then, that what has been obtained is an inexpensive,simply constructed boiler which is not only easy to erect by partialassembly in the manufacturing plant and finish erection in the field butwhich is easy to maintain during its lifetime. All of the headers arereadily accessible from their ends and no one header is of any verygreat length. The superheater tubes are, of course, drainable at thebottom and the flow arrangement which is staggered by means of thedividing walls in the headers assures even distribution of steam flow tothe superheater tubes. The arrangement of the superheater in this waymeans that there is high steam velocity, high mass flow circulation,thus maintaining safe metal temperatures. The superheater is acombination of a radiant and convection type which serves to maintain afiat steam temperature characteristic curve from 30% to of full load.The fact that the tubes are drainable simplifies the startup proceduresin the boiler. The symmetrical design of the present steam generatingunit assures uniform heat absorption through the entire system. Gasesflow over the superheater surfaces in three cross-flow patterns and theboiler banks are of the two-pass vertical flow design with cross-flow atentrance, top, and lower exists. Gas pass baflles are all weldedwater-cooled panels and are an integral part of the boiler convectionsystem. The boiler is fully water-cooled and all Welded, using apanelized construction which encloses the entire unit from the furnacefront to the rear wall of the boiler convection passes. This reducesboiler and furnace wall heights as well as foundation requirements. Eachfurnace side wall panel has its own top and bottom headers and theheaders are arranged in an offset staggered arrangement for easy accessfor inspection and cleaning.

It is obvious that minor changes may be made in the form andconstruction of the invention without departing from the material spiritthereof. It is not, however, de-

sired to confine the invention to the exact form herein shown anddescribed, but it is desired to include all such as properly come withinthe scope claimed.

The invention having been thus described, what is claimed as new anddesired to secure by Letters Patent 1s:

1. A steam generating unit, comprising (a) a furnace having a front, arear, two sides, a bottom, and a roof wall defining a combustionchamber, the rear wall consisting of two vertical sections joined by aninclined portion,

(b) a boiler including a plurality of tubes adapted to receive hotproducts of combustion from the combustion chamber,

(0) a plurality of tube panels lining the inner surface of the sidewalls, each panel having a lower inlet header and an upper outletheader, each group of lower headers and each group of upper headersbeing located laterally of one another, so that access is available toeach end of each header, and

(d) a superheater consisting of a plurality of tube panels extendingvertically in planes lying between the two vertical portions of the rearwall, the panels extending through the inclined portion and beingsubstantially supported thereby against lateral movement.

2. A steam generating unit as recited in claim 1, wherein thesuperheater is provided with two parallel transverse headers locatedbelow the bottom wall, each tube of the superheater being of generallyhair-pin shape with one end connected to one header and the other endconnected to the other header, the bight residing adjacent the roofwall.

3. A steam generating unit as recited in claim 2, wherein thesuperheater headers are provided with dividing walls to cause flow ofsteam seriatim through several sections of the superheater.

4. A steam generating unit as recited in claim 2, wherein adesuperheater apparatus enters one end of one of the headers, theapparatus consisting of a pipe that extends coaxially into the headerand is provided with radially-extending spray nozzles, each of which isdirected into a superheater tube.

5. In asteam boiler, the combination including a plurality of tubessecured together in closely spaced parallel relationship to form atleast a portion of a furnace wall, a group of adjacent ones of saidtubes being bent out of the lane of said wall in the vicinity of one endthereof so that the ends of said group of tubes are laterally displacedfrom the corresponding ends of the other tubes, a pair of headersextending along said one end of said furnace wall, one of said headershaving the laterally displaced ends of the tubes in said group connectedthereto, and the other header having the corresponding ends 'of theother tubes connected thereto.

6. A combination according to claim 5 wherein said plurality of tubesfurther includes a group of adjacent ones thereof bent out of the planeof said wall in the vicinity of the other end thereof and a further pairof headers connected to the other end of said tubes in a manner similarto the connection of said tubes to said one and said other header.

References Cited UNITED STATES PATENTS 1,760,118 5/1930 Crane 1222353,003,482 10/1961 Hamilton et al. 122478 3,007,459 11/1961 Koch 122406FOREIGN PATENTS 1,089,473 9/ 1954 France.

880,066 10/1961 Great Britain.

KENNETH W. SPRAGUE, Primary Examiner US. Cl. X.R. 122--235, 510

